Quinquagenarian is a term that refers to a person who is in their fifties, but there are many other words that can be used to describe someone in this age range. Some synonyms for quinquagenarian include fifty-something, middle-aged, and halfway to a century. Other options include over-the-hill, mature, seasoned, and wise. When describing someone in their fifties, you could also use the phrases "in their prime," "experienced," or "having reached their full potential." No matter which term you choose, it's important to remember that age is just a number and shouldn't define someone's worth or ability.